Teac A-4000

Four heads, two directions, one eddy-current motor at each reel table - Teac's late-'60s answer to the auto-reverse problem.

Overview

The A-4000 is a quarter-track stereo open-reel deck with a transport that never asks the listener to get up. It has four heads: erase, record, forward playback and reverse playback. That lets it read tape in both directions without flipping a reel. Teac's own service documentation describes the motors this way: a single dual-speed hysteresis motor drives the capstan, and two torque motors handle the reel turntables. Collectors tend to notice the reel motors first. They are eddy-current types, the same family Teac was advertising in its late-'60s line as evidence of serious transport engineering.

Reel capacity tops out at 7 inches, which puts the A-4000 in the home rather than the studio. Speeds are 7½ and 3¾ ips. The deck uses the NAB equalization curve at the higher speed and the EIA curve at the lower one. Wow and flutter, per the manufacturer's own figures, runs 0.12% at 7½ ips and 0.15% at 3¾ ips. Those numbers are respectable for the period but not spectacular. A 0.12% figure showed up across Teac's consumer line in these years, and the A-4000 sits squarely in that company.

Frequency response is quoted at 30 to 20,000 cycles at 7½ ips, with the ±3 dB window tightening to 50 to 15,000 cycles. At 3¾ ips the range narrows to 40 to 12,000 cycles overall, with the flat window at 50 to 7,500 cycles. That is the cost of halving tape speed, and Teac printed it plainly. Signal-to-noise is 50 dB at 7½ ips, unweighted, measured from peak record level. Channel-to-channel crosstalk is held to 50 dB at 1,000 cycles, with 40 dB between adjacent tracks at 100 cycles.

The deck's input and output side is built around the companion RA-40 record amplifier, a separate unit that the service literature lists at 10 lbs on its own. The RA-40 carries the microphone inputs at 10,000 ohms impedance, 0.25 mV minimum, and the line inputs at 100,000 ohms and 0.14 V minimum. Output is specified as 12 volts into a load of 100,000 ohms or more. The front panel has dual level controls whose inner and outer knobs are friction-coupled, so channels can be moved together or independently. It also has separate VU meters for each channel, per-channel record pilot lamps, a monitor selector that switches between source and tape, and a headphone jack. The record selector buttons, playback level control and the DIN-standard record/play jack round out the connections. A 2-ampere fuse protects the amplifier.

Power requirements cover 100, 117, and 200 VAC at 50 or 60 cycles. The A-4000 draws 100 VA, less than the A-4010's 110 VA, a difference that reflects the smaller chassis. The A-4000 measures 17¼ by 13 by 9½ inches and weighs 37 lbs. The RA-40 measures 17¼ by 5-5/16 by 9¼ inches. Within the same family, the A-4010L and A-4010 share the A-4000's width but stretch to 17½ inches deep and 9½ inches tall. They weigh more too, at 40 and 48 lbs respectively.

A service bulletin in the manual notes that head alignment changed at serial number 8354, with the revised geometry documented in a new figure. Anyone buying a used A-4000 should check which side of that break the unit falls on, because alignment specs and replacement head positioning differ between the two.

Period coverage of the A-4000 specifically is thin. The archive's magazine holdings turn up directory listings for adjacent Teac models rather than a full test report on this deck. Tape Recording (January 1969, p.52) listed the Teac 910 mono portable with a 0.12% wow-and-flutter figure and a 50 dB signal-to-noise ratio at 7½ ips - the same numbers the A-4000's manual quotes. That repetition across different models suggests these were house specifications Teac applied broadly across its late-'60s line, not measurements taken from any one machine. No independent lab test of the A-4000 has surfaced in the archive, and no original list price is documented here.

Maintenance follows the usual open-reel routine. The manual calls for cleaning the heads after every eight to ten hours of use. That means carbon tetrachloride or alcohol on a lintless cloth, wiped across each head face and the tape guides to strip away dirt and magnetic oxide. The point is to prevent high-frequency loss and incomplete erasure. Periodic demagnetization of the heads is also specified, with a warning to keep the demagnetizer well away from the level meters, since proximity can permanently damage them. The troubleshooting section flags bad contacts on the RL-4 relay as a cause of crosstalk in playback, which is a cheap fix if a unit develops channel bleed.

The A-4000's appeal today is the auto-reverse convenience and the eddy-current reel motors. It is not a studio machine and never pretended to be. 7-inch reels and a 50 dB S/N ratio put it in the home listening and casual recording bracket. It is a well-documented deck, though, and the service manual's level-setting and frequency-response procedures are detailed enough that a careful owner can keep one aligned. The RA-40's separate chassis also means the amplifier section can be serviced or swapped without pulling the transport.